Readout device

ABSTRACT

In a device for reading the position of a meter pointer or other indicator having a reflective portion and moving in a predetermined path, light is directed at such path from one side, for example, through the meter&#39;&#39;s cover glass, for reflection back through the glass at the position of the pointer, a series of light receiving elements of light transmitting fibers have ends thereof arranged sequentially along the path to selectively receive the light reflected at the position of the pointer and to selectively illuminate photocells to which the other ends of such elements extend, and an electrical characteristic, such as the frequency, of a signal adapted for transmission to a remote station is determined in dependence upon the selective illumination of the photocells and hence according to the position of the pointer.

United States Patent Inventor Jersey Edison, NJ.

READOUT DEVICE 19 Claims, 6 Drawing Figs.

US. 340/188, 340/190, 340/ 179, 340/208, 250/227 Int. G08c 9/06 Field ofSearch 340/ 190, 188; 250/227 References Cited UNITED STATES PATENTS2,491,591 12/ 1949 Sweeny et al 340/ 190 3,335,367 8/1967 Skooglund etal. 250/227 Primary Examiner-Thomas B. l-labecker Attorneys-Albert C.Johnston, Robert E. Isner, Lewis H.

Eslinger and Alvin Sinderbrand ABSTRACT: In a device for reading theposition of a meter pointer or other indicator having a reflectiveportion and moving in a predetemiined path, light is directed at suchpath from one side, for example, through the meters cover glass, forreflection back through the glass at the position of the pointer, aseries of light receiving elements of light transmitting fibers haveends thereof arranged sequentially along the path to selectively receivethe light reflected at the position of the pointer and to selectivelyilluminate photocells to which the other ends of such elements extend,and an electrical characteristic, such as the frequency, of a signaladapted for transmission to a remote station is detennined in dependenceupon the selective illumination of the photocells and hence according tothe position of the pointer.

PATENTED APR 6I97l 3573.773

sum 1 BF 3 IN VEN TOR EDWARD W. OHANLON ATTORNEY PATENTED m 6197| SHEET3 [JF IN VEN TOR EDWARD W. OHANLON 6 P P P P Am dmq Aha .HQQ A a un 0Qun um un o U Q SOT Tr Q UQ A UQ U A T TORNE Y READOUT DEVICE Thisinvention relates generally to readout devices for sensing the positionof a movable indicator member, such as a meter pointer or the like, andfor producing a signal which corresponds to the sensed position and maybe conveniently transmitted to a remote location where the movements areto be monitored or recorded.

In previously proposed readout devices having a mechanical, magnetic orelectrostatic coupling with the movable pointer or other member forfollowing the movements thereof, such coupling loads the pointer andthereby either affects the position thereof, and hence the accuracy ofthe indication of the condition or physical phenomenon being metered, oraffects the speed with which the pointer is displaced in response to achange in the metered condition.

Accordingly, it is an object of this invention to provide a readoutdevice for sensing or reading the position of a meter pointer or otherindicator member movable in a predetermined path and for producing anelectrical signal corresponding to the sensed position, without loadingsuch pointer by either a mechanical, magnetic or electrostatic couplingtherewith.

Another object to provide a readout device which can be attached to anyexisting meter without modification of the latter, and which can senseor read the position of the meter pointer through the usual cover glassof the meter so that there is no need to open the meter casing forinstallation readout device.

Still another object is to provide a readout device which senses orreads the position of a meter pointer through the cover glass of themeter and produces a corresponding electrical signal that can betransmitted to a remote location where pointer movements are to bemonitored or recorded, and which still permits the usual direct visualreading of the pointer position at the site of the meter.

A further object is to provide a readout device with relatively simplearrangements by which large numbers of sensed positions of a meterpointer or other movable member may be accurately discriminated fromeach other to correspondingly determine an electrical characteristic ofthe output signal from such device.

In accordance with an aspect of this invention, a readout devicecomprises means, preferably in form of a light source and a series ofoptical fiber elements simultaneously and equally receiving light fromsuch source, to emit light toward the path of movement of a pointer orother movable indicator member in a pattern that extends along the path,a series of light receiving optical fiber elements having first endsarranged at sequential positions along the path of movement toselectively receive light from the light emitting elements by way of themovable pointer, as by reflection from the latter, when the pointer isat corresponding positions in such path, a number of photocells havingthe other ends of the light receiving elements extended thereto so as tobe selectively illuminated in correspondence with the position of thepointer, and signal producing circuits having the photocells includedtherein to determine the frequency or other electrical characteristic ofthe produced signal according to the pointer position.

It is a feature of this invention, particularly in the case of a devicefor reading, through the cover glass of a meter, the position of themeter pointer moving in a plane parallel to the cover glass between thelatter and a dial face, to space apart the ends of the optical fiberelements which respectively emit the light and receive the lightreflected by the pointer, so that the distance between such end, in thedirection transverse to the path of movement, subtends the angle betweenthe light rays incident to, and reflected from the pointer, whereby toavoid the collection by the light receiving elements of light raysreflected from the dial face.

In accordance with another feature of this invention, the electricalcharacteristic of the output signal is controlled in accordance with thetotal effective resistance value of a series string of resistanceelements associated with the photocells and each having a diode inparallel therewith, and a source of potential is connected to thejunctions between the successive resistance elements through theassociated photocells so that, upon illumination of a selected photocellcorresponding to the position of the pointer, the potential at thecorresponding junction is varied in relation to the potentials at theother junctions to cause current to flow through the diodes which arebetween such junction of varied potential and an end of the string foreffectively eliminating from the total resistance of the string thevalues of the resistance elements in parallel with the currentconducting diodes.

The above, and other objects, features and advantages of this invention,will be apparent in the following detailed description of anillustrative embodiment which is to be read in connection with theaccompanying drawings, wherein;

FIG. 1 is a front elevational view of a typical meter having a readoutdevice according to this invention affixed thereto;

FIG. 2 is an enlarged sectional view taken along the line 22 on FIG. I;

FIG. 3 is a sectional view taken along the line 3-3 on FIG. 2;

FIG. 4 is a further enlarged detail sectional view taken along the line44 on FIG. 2;

FIG. 5 is a partial schematic view illustrating the connections betweenoptical fiber elements and photocells in the readout device according tothis invention;

FIG. 6 is a fragmentary diagrammatic view for illustrating the manner inwhich a resistance value is varied in dependence on illumination of aselected photocell; and

FIG. 7 is a diagrammatic illustration of circuits by which an electricalcharacteristic of an output signal is varied in accordance with theposition of the meter pointer as represented by the illumination ofselected photocells.

Referring to the drawings in detail, and initially to FIGS. 1 and 2thereof, it will be seen that a readout device 10 according to thisinvention is there shown associated with a conventional meter 11 havinga housing I2 with a cover glass 13 at the front to permit direct, visualreading of the position of a pointer 14 in relation to a suitablycalibrated scale 15 on a dial face 16 (FIG. 2) lying in back of theplane of movement of the pointer. The meter 11 is shown to be of thetype in which its pointer 14 is angularly displaced, for example,through an arc of 270, to move the pointer end along the arcuate scale15 from its zero to full indication upon similar turning of itssupporting shaft I7 in response to variations in the metered conditionor physical phenomenon, such as, a liquid level, or a temperature,pressure or the like.

For association with the illustrated meter 11, the readout device 10 isshown to comprise a cylindrical casing 18 having a diametersubstantially smaller than that of the arcuate scale 15 so that, whencasing 18 is secured at one end to cover glass I3 in alignment with theaxis xx of shaft 17, such casing will not interfere with the directvisual reading of the indication provided by the free end of pointer 14in cooperation with scale 15. The casing 18 may be secured, at its end,to cover glass 13 by a suitable epoxy resin after axial alignment of thecasing with respect to shaft 17 is ensured by a template (not shown)provided for that purpose. Upon setting of the epoxy resin or cement andremoval of the locating template, casing 18 may be further secured tometer 11 by means of wires 19 (FIG. I) which extend at right angles toeach other across the forward end of the casing and have their endswound around, or otherwise secured to the usual screwheads 20 on meterhousing 12.

In accordance with this invention, readout device 10 generally comprisesmeans 21 emitting light from casing 18 toward the path of movement ofpointer 14 in back of cover glass 13 in a pattern that extends alongsuch path so that, at each position of pointer 14, such light will bereflected, at least by a reflective portion 22 on pointer 14, to passforwardly through cover glass 13 (FIG. 2).

As shown, light emitting means 21 is preferably constituted by a singlelight source 23 mounted within casing 18 in a holder 24 and beingsupplied with energizing current from an external supply by way ofconductors in a cable 25 extending from casing 18, and a series ofelongated light emitting elements 26. Each element 26 is composed of alarge number of glass or other light transmitting fibers or filaments 27bundled together in a flexible plastic sheath 28 (FIG. 4) so that lightadmitted to fibers 27 at one end of each element 26 will be transmittedtherealong irrespective of bends formed in the element and projectedlongitudinally from the other end of the light emitting element. Theends 260 ofelements 26 which are to receive light from source 23 aremounted in a circular array in a annulus 29 extending from holder 24around source 23 so that such ends simultaneously receive an equalquantum of light energy. The other or light emitting ends 26!; ofelements 26 are arranged at sequential positions along the path ofmovement of pointer 14, and particularly of its reflective portion 22.When the path ofmovement of reflective portion 22 is a circular are, asshown, the ends 26b of light emitting element 26 are arranged in aconcentric similar circular arc (FIG. 3), for example, by being suitablyanchored in an annulus or end wall 31) adjacent the end of casing 18secured to cover glass 13. The arc along which element ends 2611 areranged preferably has a smaller radius than the arcuate path of movementof reflective portion 22, and ends 26b angled outwardly with respect toaxis x-x so that light rays emitted from each of ends 26b will passthrough cover glass 13 to impinge on, and be reflected from portion 22or pointer 14 when the latter is at a corresponding position in itsarcuate path.

The readout device in accordance with this invention further comprises aseries of elongated light receiving elements 31 which may be similar toelements 26 and hence composed of a bundle of light transmitting fibersin a flexible plastic sheath. Ends 31a of elements 31 are arranged atsequential positions along the path of movement of reflective portion 22of pointer M to selectively receive light reflected from portion 22 wenpointer 14 is correspondingly positioned in its path of movement. In theembodiment shown, ends 31a are anchored in annulus or end wall 30 alonga circular arc (FIG. 3) which is concentric with, and of larger radiusthan the arcuate path of reflective portion 22 so that the radialdistance between ends 26b and 31a subtend the angle a (FIG. 2) enclosedby light rays from light emitting elements 26 which are incident onreflective portion 22 and reflected from the latter toward lightreceiving elements 31, in other words, the radial dance between elementends 26b and 31a is equal to two times the produce of the distancebetween the plane of movement of pointer 14 and the plane of ends 26band 31a and of the tangent of the angle (12/2) enclosed by the lightrays from ends 26b and the normal or perpendicular to the plane ofmovement of the pointer. Further, each end 310 is angled inwardly withrespect to axis x-x, as shown on P16. 2, so that light rays reflectedfrom reflective portion 22 will be aligned with the axis of each element31 at its end 310 for optimum transmission by the light receivingelement.

By reason of the foregoing, only that element 31 having its end 31adisposed at a position corresponding to that of the pointer 14 willreceive light emitted from an element 26 by way of reflection fromportion 22 of the pointer, as illustrated at the left-hand side of FIG.2, and the remaining light emitted from elements 26 will be incident ondial face 16 which, in being spaced rearwardly from the plane ofmovement of pointer 14, will cause the incident light to travel a longerpath and thereby reflect such light forwardly through cover glass 13 topositions spaced radially outward from the ends 31a at positions that donot correspond to that of the pointer, as illustrated at the right-handside of FIG. 2. It is also preferred that the dial face 16 be ofrelatively low reflectivity so that light from elements 26 and ambientlight will not be strongly reflected therefrom, particularly intoelement ends 31a. For any position of pointer 14 between its zero andfull-scale indications with respect to scale 15, only a correspondinglypositioned one of elements 31 will receive reflected, relatively intenselight for transmission therealong to indicate the presence of thepointer at such position.

1f the position ofthe meter pointer 14 has to be readout with anaccuracy within 1 percent of its actual position, that is, to within 27of its actual position within its 270 arc of movement, this can easilybe achieved by providing elements 31 having their ends 31a equallyspaced along an arc of 270. lfeaeh element 31 has a diameter ofapproximately 0.02 inch, then the minimum diameter of the arc of 270 inwhich the ends 31a of 100 of such elements can be arranged will beapproximately O.84 inch, from which it is clear that casing 18 canreadily be provided with a diameter substantially smaller than that ofscale 15, as previously indicated to be desirable.

It will be apparent that the reflection of light from portion 22 ofpointer 14 to direct light selectively into the end 31a of that element31 which corresponds to the position of the pointer in no way loads thepointer and thus does not affect either the accuracy with which pointer14 indicates the metered condition or the speed with which pointer 14can move to indicate a change in the metered condition. The transmissionof light along one of elements 31 corresponds to an on" condition andindicates the presence of pointer 14 at the corresponding position inrelation to scale 15, while the remaining elements 31 do not transmitlight and thus are in an ofF condition to indicate the absence of thepointer from the corresponding positions on scale 15.

In accordance with this invention, light receiving elements 31 extend tophotocells PC which detect the on or off condition of the respectivelight receiving elements, that is, whether such elements 31 aretransmitting or are not trans mitting light, and correspondinglydetermine the characteristic of an electrical signal so that suchcharacteristic represents the position of pointer 14. Of course, each oflight receiving elements 31 could lead to an individual photocell but,in the case of a readout device having one hundred elements 31, thiswould require 100 photocells. Since the 100 elements 31 correspond topointer positions that may be numbered from 0 to 99, inclusive, each ofthe numbered positions may be represented by a number in the units from0 to 9 to which there is added a number in the tens from O0 to 90.Similarly, the photocells for association with the lOO elements 31 maybe divided into two groups or sets PC and PC, each having l0 photocellstherein and respectively representing units and tens, and each element31 leads to that one photocell in the units set and that one photocellin the tens set which together represent the number of the pointerposition to which that particular element 31 corresponds. For example,as shown in HO. 5, the elements 31 representing the positions 0 to 9,inclusive, of the pointer are respectively connected to the 0 to 9 PCphotocells in the units set and each to the PC photocell in the tensset; the elements 31 representing the positions 10 to 19 of the pointerare respectively connected to the 0 to 9 PC photocells in the units setand each to the 10 PC, photocell in the tens set; and the remainingelements 31 are similarly each connected to one of the units photocellsPC and to one of the tens photocells PC, in accordance with the numberof the pointer position to which the element 31 corresponds. Thus, eachof the photocells has a cluster of ten elements leading thereto.

The connection of each of light receiving elements 31 to one photocellin the units set and to one photocell in the tens set is easily effectedby dividing the bundle of fibers or filaments making up such element 31into two branches 31b (F 1G. 2) which are separately sheathed and leadto the respective photocells in the two sets.

When all of the elements 31 leading to a photocell are in the off ordark condition, such photocell has a relatively high electricalresistance, for example, of l M ohm, and such resistance drops, forexample, to 10 K ohm, when any one of the elements 31 leading to thephotocell is transmitting light thereto, that is, in the on condition.In accordance with this invention, the photocells PC and PC, areincluded in a signal producing circuit so that an electricalcharacteristic of the produced signal is determined or varied by 100increments in dependence upon the described selective illumination ofthe photocells and the resistance changes therein, thereby to convertthe analog meter reading into a digital presentation that can betransmitted to a remote. monitoring or data processing station.

Referring to FIG. 7, it will be seen that the circuit there illustratedincludes two series strings of units resistors R R R R -R,, and tensresistors R R R R R which strings are connected in series with eachother through a re-' sistor 32. The resistors Il -R each have a value torepresent a unit, and each of the resistors R -R is weighted torepresent a tens, that is, has a value 10 times that of each unitresistor R -R Connected in parallel with the unit resistors R,,R,, andthe tens resistors R,,,,R., are diodes D,,--D and diodes D -Drespectively. The diodes D,,D and diodes D -D respectively. The diodesD,,-D are all arranged to conduct current in one direction, that is, inthe direction from the end of the respective series string of resistorR,,-R connected through resistor 32 with the other series string ofresistors R ,,R The diodes D D are also arranged to conduct current inone direction away from the end of the respective series string ofresistors which is connected with resistor 32, that is, in the directionopposed tothe current conducting direction of diodes D -D The junctionsJ,,--J which follow the resistors identified by the correspondingsubscripts in the series string of resistors R -R considered in theconducting direction of the respective diodes D,,D are connected, at oneside, to a source of potential, for example, -10 V. DC, through therespective photocells PC for units 0 to 9 and, at the other side, toground through equal resistors 33. Similarly, the junctions J ,,J whichfollow the resistors identified by the corresponding subscripts in theseries string of resistors R,,,,--R considered in the conductingdirection of the respective diodes D -D are connected, at one side, tothe l0 V. DC source through the respective photocells PC, for tens 00 to90 and, at the other side, to ground through equal resistors 33. Thearrangement is such that illumination of a units photocell PC throughone of the elements 31 extending thereto causes the resistance values ofthe associated units resistor and of all other units resistors of lowernumerical significance to be substantially switched out of the seriesstring of units resistors and, similarly, the illumination of a tensphotocell PC, causes the resistance values of the associated tensresistor and of all other tens resistors of lower numerical significanceto be substantially switched out of the series string of tens resistors.Thus, the total resistance of the two series strings of resistors willbe determined by which of the photocells associated with such stringsare illuminated, and the resistor 32 will determine the minimum totalresistance.

The effect of each photocell in substantially switching out itsassociated units or tens resistor and the units or tens resistors oflower numerical significance will now be explained with reference toFIG. 6 which merely illustrates that portion of the circuit of FIG. 7made up of the units photocells corresponding to the units 1 and 2, theunits resistor R and the parallel diode D For the purpose of thisexplanation it will be assumed that the circuit components shown havethe following typical values:

Photocells PC 1 and 2;

PCR (resistance when dark)l M ohm;

PCR (resistance when light or illuminated-10 K ohm.

Resistors R and each of the resistors 33 has a value of 1 M ohm.

Diode D has an unbiased or no current resistance R of 10 M ohm, and aresistance value R of 50 K ohm when forwardly biased, that is, whencurrent flow therethrough.

When neither of the units photocells l and 2 is illuminated, that is,when the meter pointer is not adjacent ends 31a of any of the elements31 extending to such cells, both cells 1 and 2 will have the samerelatively high resistance so that junctions J and Jr, will be at thesame potential and no current flows in diode D With the typical valuesgiven above, the total resistance R of the parallel resistor R and diodeD is:

R .909M ohm EJFTIOETF Thus, the potential at J will have a largernegative value than the potential at J l and diode D will be forwardlybiased, that is, current will flow from J l to J establishing apotential difference between J, and J of approximately 0.5V. Thus, if Jhas a potential of 9.9V, the potential at J will be 9.4V.

The voltage-current relationship on diode D will establish the effectiveresistance value R thereof of 50 K ohm. Hence, the resultant R, of theresistance value of resistor R and of the conducting resistance of diodeD in parallel, will be:

=45K ohm (approx.)

Thus, when photocell 2 is dark or does not receive light from anassociated element 31, its related resistor R has an effective value of500 K ohm, and such effective value is switched out or reduced to lessthan 50 K ohm upon illumination or impingement of light on photocell 2.

It will be apparent that, when the potential at junction J 1 is reducedfrom the normal value of 5.0 V to 9.4 V, as described above, the resultis to forwardly bias diode D and cause current flow therethrough fromthe relatively higher potential at junction J (FIG. 7) to the reducedpotential at J and such current flow through diode D, similarly reducesthe resultant resistance of resistor R and diode D,, in parallel, fromapproximately 500 K ohm to less than 50 K ohm. Thus, when any one ofunits photocells PC 0 to 9 has light impinging thereon, there is aneffective resistance reduction of approximately 450 K ohm for theassociated units resistor and for each units resistor signifying a lowerunit. For example, if units photocell PC 6 has light directed thereto byan associated element 31, the effective resistance of resistor R will bereduced from 500 K ohm. to less than 50 K ohm, and the effectiveresistance of each of resistors R to R inclusive, will be similarlyreduced by approximately 450 K ohm. Since the effective resistance ofresistor R is reduced by 450 K ohm when units photocell PC 0 isilluminated, the resistance change resulting from illumination ofphotocell PC 6, as compared with illumination of photocell PC 0, is6X45O K ohm, that is, a change of 2.7 M ohm. further, it will beapparent that, as pointer 14 moves past ten successive positions, thetotal resistance of the series string of resistors R,,-R will change inincrements of 450 K ohm.

As previously mentioned, each of the tens resistors R -R is weighted tocorrespond to the total resistance of the resistors R,,R in the unitsstring. Thus, for the values given above, the illumination of each ofthe tens photocells PC, will result in a reduction of the effectiveresistance of its associated resistor and of each of the tens resistorssignify all lower tens by 4.5 M ohm. For example, if tens photocell PC,30 is illuminated, the resistance of the associated resistor R and ofeach of the lower resistors R R and R in the same series string will bereduced by 4.5 ohm for a total resistance reduction of 13.5 M ohm ascompared with the total resistance of the tens string when the photocellPC, 00 is illuminated.

Since the diodes D -D in the tens string are conductive in the directionopposed to the conductive direction of the diodes D,,D in the unitsstring, it will be apparent that the illumination of a photocellassociated with one string cannot influen'ce the flows of current in thediodes of the other string.

Further, it will be apparent that, at any time, the total resistance ofthe units and tens strings of resistors R R and R -R corresponds to theposition of pointer 14 and to the element 31 which receives reflectedlight from such pointer for transmission to that one of the unitsphotocells and to that one of the tens photocells which togetherrepresent the pointer position.

It will be apparent that the incremental change in the total resistanceof the series strings in correspondence with the positional change ofthe meter pointer may be readily employed to vary any desiredcharacteristic, for example, frequency, voltage, ,etc. of a producedelectrical signal for transmission to a remote station at which themeter reading is to be monitored, recorded or subjected to dataprocessing procedures.

In the arrangement of FIG. 7, the total resistance of the se riesstrings of units and tens resistors R ,-R and R -R is used to vary theresistance of an RC oscillator and thereby determine the outputfrequency of the oscillator. Such RC oscillator is preferably a WienBridge Oscillator which desirably exhibits very stable frequencyoperation because of the nature of its feedback circuit. As shown, thestrings of units and tens resistors are connected in parallel with acapacitor C to form a parallel RC network which is connected to the gateat a field effect transistor (not shown) constituting the input to anelectronic amplifier 34. A series RC network constituted by a resistanceR and a capacitor C is also connected to such input to amplifier 34.These parallel and series RC networks together with the illustratedfeedback networks CF RF,, RD and R around the amplifier loop form aconventional Wien Bridge Oscillator. The series and parallel RC networksform a high pass and low pass filter whose corner frequency is fixed bythe R and C values of such networks. This arrangement provides afrequency feedback which has a narrow pass frequency, and the voltagefeedback controls the amplitude of oscillation. Both the frequency andvoltage feedback circuits are positive thus initiating oscillations. Inaddi tion to such positive feedback circuits, there is provided anegative feedback loop to ensure that overdrive is now applied.

Thus, the output obtained from the Wien Bridge Oscillator has afrequency which is dependent upon the total resistance of the seriesstrings of units and tens resistors, that is, the resistance in theparallel RC network, and the range of such frequency, which obviouslycorresponds to the position of pointer 14, may be varied, bysimultaneously changing the values of C and C so as to make the outputof the oscillator suitable for transmission to a remote station, forexample, by way of usual telephone lines.

lt will be apparent in the foregoing description of readout device It)that the operation thereof is predicated on the (m off, that is, digitalvariation of the light intensity in the elements 31. in other words,each unit variation in the reading of meter 11 discontinues thetransmission of light by one of elements 31 and initiates thetransmission of light by another of such elements 31, and this, inturn,causes corresponding change in the condition of associated photocells.The speed with which such changes in the conditions of the photocellsmay occur is practically limited only by the speed of movement of themeter pointer 14, as the readout device l0 itself has an upper changefrequency limitation of approximately 50 kilohertz.

A digital response is obtained from the readout device as it has afinite number of light receiving elements 31 for detecting the positionof the meter pointer. Having obtained a digital output from thephotocells, which output is related to the position of the meter pointeror other movable member being read, the format to be generated by theoutput of the photocells is selected in dependence upon the speed,accuracy, repeatability and complexity of the movement being read. Thus,the fomtat for the information to be transmitted may be of lowsinusoidal frequency, as in the embodiment described in detail herein,low or high frequency carrier modulation, time differential, digitalcode, pulse width modulation, high sinusoidal frequency and multiplemodes. The format selected for the information to be transmitted ofcourse determines the means by which such transmission may be effected.For example, where the low sinusoidal frequency, low frequency carriermodulation or time differential format is selected, transmission can beby telephone line. However, where the digital code, pulse widthmodulation or multiple mode is the selected format, transmission bycoaxial cable is required. Transmission may also be ny radio frequencytransmission, microwave transmission, power lines, laser beam or anyother means employed for information transmittal.

Although a particular embodiment of the invention has been described indetail herein with reference to the accompanying drawings, it is to beunderstood that the invention is not limited to that precise embodiment,and that various changes and modifications may be effected therein byone skilled in the art without departing from the scope or spirit of theinvention as defined in the appended claims,

I claim:

1. A readout device for optically sensing the position of an indicatormember movable in a predetermined path and for producing an electricalsignal corresponding to the sensed position, comprising means emittinglight along the length of said path, a plurality of light receivingelement each composed of light transmitting fibers and having first endsthereof arranged at sequential positions adjacent to the length of saidpath to selectively receive light from said light emitting means by wayof said indicator member when the latter is at cor responding positionsin said path, a plurality of photocells having the other ends of saidlight receiving elements extending thereto so as to be selectivelyilluminated when said member is disposed at said positions correspondingto the associated light receiving elements, and signal producing circuitmeans includ ing said photocells to determine an electricalcharacteristic of the produced signal in dependence upon the selectiveillumination of said photocells and hence according to the posi tion ofsaid indicator member.

2. A readout device according to claim 1, in which said light emittingmeans and said first ends of the light receiving elements are disposedat the same side of said path, and at least a portion of said indicatormember is reflective so that, in each of said positions of the indicatormember, said portion thereof reflects light from said light emittingmeans into the cor respondingly positioned first end ofa light receivingelement.

3. A readout device according to claim 2, in which said light emittingmeans includes a light source and a series of light emitting elementseach composed of light transmitting fibers and having first endssimultaneously and equally receiving light from said source and theirother ends directed toward said path and arranged sequentiallytherealong.

4. A readout device according to claim 3, in which said indicator memberis a meter pointer movable in said path, and said path is in a planebetween a coplanar dial face and cover glass, and said light emittingand light receiving elements respectively emit and receive light throughsaid cover glass.

5. A readout device according to claim 4, in which said first ends ofthe light receiving elements are spaced from said other ends of thelight emitting elements in directions transverse to said path bydistances that substantially subtend an angle enclosed by light raysincident on said reflective portion from said light emitting elementsand reflected from said portion toward said light receiving elements.

6. A readout device according to claim 4, in which said pointer ismovable angularly so that said path of its reflective portion is acircular arc and said first ends of the light receiving elements andsaid other ends of the light emitting elements are arranged in similarareas of larger and smaller radii and then the radius of said path so asto be spaced radially by distances that substantially subtend an angleenclosed by light rays from said light emitting elements incident onsaid reflec' tive portion and reflected from the latter toward saidlight receiving elements, whereby light rays from said light emittingelements impinging on said dial face are reflected radially away fromsaid first ends of the light receiving elements.

ill

7. A readout device according to claim 6, in which said reflectiveportion of the pointer is spaced radially inward from a free end of thepointer which cooperates with a scale on said dial face for visuallyindicating the position of said pointer, and said light source, lightemitting and light receiving elements and photocells are contained in acylindrical casing which is secured to said cover glass anddiametrically dimensioned to be radially inside said scale, whereby toavoid interference with direct visual reading of the position of thepointer.

8. A readout device according to claim 4, in which said dial face is ofrelatively low reflectivity.

9. A readout device according to claim 1, in which there are at leasttwo sets of said photocells and said other end of each light receivingelement extends to a respective photocell in each of said sets, wherebythe number of said light receiving elements and of said positions of themember that can be dis criminately sensed is the product of the numbersof said photocells in said sets.

10. A readout device according to claim I, in which said circuit meansincludes a series arrangement of resistance elements connected with saidphotocells so as to have the resistance values thereof selectivelyswitched out of said series arrangement in turn upon selectiveillumination of said photocells, whereby the total resistance of saidseries arrangement corresponds to the position of said indicator member,and means to vary said electrical characteristic of the signal inaccordance with changes in said total resistance.

11. A readout device according to claim 10, in which said circuit meansincludes an RC oscillator having said signal as the output thereof, andsaid total resistance of the series arrangement constitutes a resistancecomponent of the oscillator, whereby the frequency of said output is theelectrical characteristic of the signal which is varied according to theposition of said indicator member.

12. A readout device according to claim 1, in which said circuit meansincludes resistance elements associated with said photocells and eachhaving a diode in parallel therewith to freely conduct current in onedirection so that the resistance effect of each resistance element issubstantially eliminated when current flows in the respective diode,said resistance elements and parallel diodes are connected in at leastone series string, a source of electrical potential is applied tojunctions between successive resistance elements through said associatedphotocells so that, upon illumination of a selected photocellcorresponding to the position of said member, the potential at thecorresponding junction is varied in relation to the potentials at theother junctions to cause current to flow through all of the diodes whichare between said corresponding junction and one end of said seriesstring for effectively eliminating from the total resistance of saidstring those resistance elements in parallel with the current conductingdiodes, the values of said resistance element are selected to correspondto increments of movement of said member between said positions thereof,and means to vary said electrical characteristic of .the signal inaccordance with changes in said total resistance of the series string.

IS. A readout device'according to claim 12, in which there are first andsecond sets of said photocells each having resistance elements anddiodes associated therewith in respective series strings as aforesaid,said series strings are connected with each other in series, the diodesin one of said series strings are conductive in the direction opposed tothat in whichthe diodes of the other series string are conductive sothat'tlie diodes of each of said strings are uninfluenced by the stateof the diodes" in the other string, the value of each re sistanceelement associated with a photocell of said second set is substantiallyequal to the sum of the values of the resistance elements associatedwith the photocells of said first set, and said other end of each lightreceiving element extends to a respective photocell in each of saidfirst and second sets, whereby the number of positions of said memberthat can be discriminately sensed is the product of the numbers of saidphotocells in said first and second sets.

In combination with a meter having a pointer with a reflective portionmovable in a predetermined path lying in a plane which is between aparallel dial face and cover glass to provide, a visual indication of acondition sensed by the meter: a readout device for providing anelectrical signal corresponding to said visual indication and suitablefor transmission to a remote station, said readout device comprising acasing secured against said cover glass of the meter, means emittinglight from said casing through said cover glass toward said path alongthe length of the latter so as to be reflected back through said glassby said reflective portion of the pointer only at the position of thepointer, a series of light receiving elements in said casing eachcomposed of light transmitting fibers and having first ends thereofarranged in sequence to selectively receive the light reflected throughsaid glass from said reflective portion of the pointer when the latteris at corresponding positions in said path, a plurality of photocells insaid casing having the other ends of said light receiving elementsextending thereto so as to be selectively illuminated only when saidpointer is disposed at the positions corresponding to the associatedlight receiving elements, and signal producing circuit means having saidphotocells included therein to determine an electrical characteristic ofthe produced signal in dependence on the illumination of said photocellsand hence according to said visual indication.

15. The combination according to claim 14, in which said pointer ismovable angularly so that said path is a circular arc, said lightemitting means includes a light source and a series of light emittingelements each composed of light transmitting fibers and having firstends equally receiving light from said source and their other endsdirected toward said cover glass and arranged in sequence, saidsequentially arranged first ends of the light receiving elements andother ends of the light emitting elements lying along similar arcs oflarger and smaller radii than said are of the path so as to be spacedapart radially by a distance that substantially subtends the angle atwhich light rays from said light emitting elements are reflected by saidreflective portion of the pointer.

16. The combination according to claim 15, in which said scale istraversed by a free end of said pointer from which said reflectiveportion is substantially spaced, and said casing is disposed radiallyinward with respect to said pointer end and scale to permit reading ofsaid visual indication with said casing secured against the cover glass.

17. The combination according to claim 14, in which said dial face is ofrelatively low reflectivity.

18. The combination according to claim 14, in which there are at leasttwo sets of said photocells and said other end of each light receivingelement extends to a respective photocell in each of said sets, wherebythe number of said light receiving elements and of said positions of thepointer that can be discriminately sensed is the product of the numbersof said photocells in said sets.

19. The combination according to claim 14, in which said circuit meansincludes a series arrangement of resistance elements connected withsaid'photocells so as to have the resistance values thereof selectivelyswitched out of said series arrangement in turn upon selectiveillumination of said photocells, whereby the total resistance of saidseries arrangement corresponds to the position of said indicatorpointer, and means to vary said electrical characteristic of the signalin accordance with changes in said total resistance.

1. A readout device for optically sensing the position of an indicatormember movable in a predetermined path and for producing an electricalsignal corresponding to the sensed position, comprising means emittinglight along the length of said path, a plurality of light receivingelement each composed of light transmitting fibers and having first endsthereof arranged at sequential positions adjacent to the length of saidpath to selectively receive light from said light emitting means by wayof said indicator member when the latter is at corresponding positionsin said path, a plurality of photocells having the other ends of saidlight receiving elements extending thereto so as to be selectivelyilluminated when said member is disposed at said positions correspondingto the associated light receiving elements, and signal producing circuitmeans including said photocells to determine an electricalcharacteristic of the produced signal in dependence upon the selectiveillumination of said photocells and hence according to the position ofsaid indicator member.
 2. A readout device according to claim 1, inwhich said light emitting means and said first ends of the lightreceiving elements are disposed at the same side of said path, and atleast a portion of said indicator member is reflective so that, in eachof said positions of the indicator member, said portion thereof reflectslight from said light emitting means into the correspondingly positionedfirst end of a light receiving element.
 3. A readout device according toclaim 2, in which said light emitting means includes a light source anda series of light emitting elements each composed of light transmittingfibers and having first ends simultaneously and equally receiving lightfrom said source and their other ends directed toward said path andarranged sequentially therealong.
 4. A readout device according to claim3, in which said indicator member is a meter pointer movable in saidpath, and said path is in a plane between a coplanar dial face and coverglass, and said light emitting and light receiving elements respectivelyemit and receive light through said cover glass.
 5. A readout deviceaccording to claim 4, in which said first ends of the light receivingelements are spaced from said other ends of the light emitting elementsin directions transverse to said path by distances that substantiallysubtend an angle enclosed by light rays incident on said reflectiveportion from said light emitting elements and reflected from saidportion toward said light receiving elements.
 6. A readout deviceaccording to claim 4, in which said pointer is movable angularly so thatsaid path of its reflective portion is a circular arc and said firstends of the light receiving elements and said other ends of the lightemitting elements are arranged in similar areas of larger and smallerradii and then the radius of said path so as to be spaced radially bydistances that substantially subtend an angle enclosed by light raysfrom said light emitting elements incident on said reflective portionand reflected from the latter toward said light receiving elements,whereby light rays from said light emitting elements impinging on saiddial face are reflected radially away from said first ends of the lightreceiving elements.
 7. A readout device according to claim 6, in whichsaid reflective portion of the pointer is spaced radially inward from afree end of the pointer which cooperates with a scale on said dial facefor visually indicating the position of said pointer, and said lightsource, light emitting and light receiving elements and photocells arecontained in a cylindrical casing which is secured to said cover glassand diametrically dimensioned to be radially inside said scale, wherebyto avoid interference with direct visual reading of the position of thepointer.
 8. A readout device according to claim 4, in which said dialface is of relatively low reflectivity.
 9. A readout device according toclaim 1, in which there are at least two sets of said photocells andsaid other end of each light receiving element extends to a respectivephotocell in each of said sets, whereby the number of said lightreceiving elements and of said positions of the member that can bediscriminately sensed is the product of the numbers of said photocellsin said sets.
 10. A readout device according to claim 1, in which saidcircuit means includes a series arrangement of resistance elementsconnected with said photocells so as to have the resistance valuesthereof selectively switched out of said series arrangement in turn uponselective illumination of said photocells, whereby the total resistanceof said series arrangement corresponds to the position of said indicatormember, and means to vary said electrical characteristic of the signalin accordance with changes in said total resistance.
 11. A readoutdevice according to claim 10, in which said circuit means includes an RCoscillator having said signal as the output thereof, and said totalresistance of the series arrangement constitutes a resistance componentof the oscillator, whereby the frequency of said output is theelectrical characteristic of the signal which is varied according to theposition of said indicator member.
 12. A readout device according toclaim 1, in which said circuit means includes resistance elementsassociated with said photocells and each having a diode in paralleltherewith to freely conduct current in one direction so that theresistance effect of each resistance element is substantially eliminatedwhen current flows in the respective diode, said resistance elements andparallel diodes are connected in at least one series string, a source ofelectrical potential is applied to junctions between successiveresistance elements through said associated photocells so that, uponillumination of a selected photocell corresponding to the position ofsaid member, the potential at the corresponding junction is varied inrelation to the potentials at the other junctions to cause current toflow through all of the diodes which are between said correspondingjunction and one end of said series string for effectively eliminatingfrom the total resistance of said string those resistance elements inparallel with the current conducting diodes, the values of saidresistance element are selected to correspond to increments of movementof said member between said positions thereof, and means to vary saidelectrical characteristic of the signal in accordance with changes insaid total resistance of the series string.
 13. A readout deviceaccording to claim 12, in which there are first and second sets of saidphotocells each having resistance elements and diodes associatedtherewith in respective series strings as aforesaid, said series stringsare connected with each other in series, the diodes in one of saidseries strings are conductive in the direction opposed to that in whichthe diodes of the other series string are conductive so that the diodesof each of said strings are uninfluenced by the state of the diodes inthe other string, the value of each resistance element associated with aphotocell of said second set is substantially equal to the sum of thevalues of the resistance elements associated with the photocells of saidfirst set, and said other end of each light receiving element extends toa respective photocell in each of said first and second sets, wherebythe number of positions of said member that can be discriminately sensedis the product of the numbers of said photocells in said first andsecond sets.
 14. In combination with a meter having a pointer with areflective portion movable in a predetermined path lying in a planewhich is between a parallel dial face and cover glass to provide, avisual indication of a condition sensed by the meter: a readout devicefor providing an electrical signal corresponding to said visualindication and suitable for transmission to a remote station, saidreadout device comprising a casing secured against said cover glass ofthe meter, means emitting light from said casing through said coverglass toward said path along the length of the latter so as to bereflected back through said glass by said reflective portion of thepointer only at the position of the pointer, a series of light receivingelements in said casing each composed of light transmitting fibers andhaving first ends thereof arranged in sequence to selectively receivethe light reflected through said glass from said reflective portion ofthe pointer when the latter is at corresponding positions in said path,a plurality of photocells in said casing having the other ends of saidlight receiving elements extending thereto so as to be selectivelyilluminated only when said pointer is disposed at the positionscorresponding to the associated light receiving elements, and signalproducing circuit means having said photocells included therein todetermine an electrical characteristic of the produced signal independence on the illumination of said photocells and hence according tosaid visual indication.
 15. The combination according to claim 14, inwhich said pointer is movable angularly so that said path is a circulararc, said light emitting means includes a light source and a series oflight emitting elements each composed of light transmitting fibers andhaving first ends equally receiving light from said source and theirother ends directed toward said cover glass and arranged in sequence,said sequentially arranged first ends of the light receiving elementsand other ends of the light emitting elements lying along similar arcsof larger and smaller radii than said arc of the path so as to be spacedapart radially by a distance that substantially subtends the angle atwhich light rays from said light emitting elements are reflected by saidreflectiVe portion of the pointer.
 16. The combination according toclaim 15, in which said scale is traversed by a free end of said pointerfrom which said reflective portion is substantially spaced, and saidcasing is disposed radially inward with respect to said pointer end andscale to permit reading of said visual indication with said casingsecured against the cover glass.
 17. The combination according to claim14, in which said dial face is of relatively low reflectivity.
 18. Thecombination according to claim 14, in which there are at least two setsof said photocells and said other end of each light receiving elementextends to a respective photocell in each of said sets, whereby thenumber of said light receiving elements and of said positions of thepointer that can be discriminately sensed is the product of the numbersof said photocells in said sets.
 19. The combination according to claim14, in which said circuit means includes a series arrangement ofresistance elements connected with said photocells so as to have theresistance values thereof selectively switched out of said seriesarrangement in turn upon selective illumination of said photocells,whereby the total resistance of said series arrangement corresponds tothe position of said indicator pointer, and means to vary saidelectrical characteristic of the signal in accordance with changes insaid total resistance.